42 
THE VOYAGE OF H.M.S. CHALLENGER. 
out beyond the parapodium. Fig. 23 represents the portion of the hook-apparatus which 
extends beyond the parapodium. This part of the hook is ’2 mm. long and ‘02 mm. broad; 
the end is bent at more than a right angle and gracefully curved. There is no separate 
manubrial plate — the end of the manubrium merely becomes thinner, more flattened, and 
bent backwards, so that it embraces nearly the whole hook (ma.). The whole manubrium 
is covered by numerous tubercles, which show the powerful development of its mus- 
cular system. These chitinous parts are of a deep dark yellow and yellowish-brown 
where the light falls upon them. I have not succeeded in finding any trace of suckers. 
Host. — The single specimen was foundupon the peristome of A ntedonphalangium, Mull. , 
sp., dredged in the Minch, from 60 to 80 fathoms, August 14, 1869, by H.M.S. “Porcupine.” 
23. Myzostoma calycotyle, n. sp. (PI. III. figs. 24-26). 
The colour of the animal varies from dirty grey to brownish ; the shape of the body 
is oblong, the diameter being 3 ‘6 mm., and the length 2 mm. The convex dorsal surface 
is covered with small scattered whitish papillae, while the concave under surface is much 
bent and folded. The margin is beset with numerous cirri of ’2 mm. in length, and 
considerably bent upwards (fig. 24). The shape of the specimen renders an examination 
of the ventral side very difficult. A portion of the parapodia and suckers are squeezed 
into the furrows, so that it is quite impossible to examine them properly, which is much 
to be regretted, since the type is an interesting one. In the first place, the suckers are 
not situated, as is usual, between the parapodia, but arise quite near their base (fig. 26). 
The suckers (s.) are distinguished by being very strongly developed ; their shape is 
also peculiar ; they closely resemble stalked goblets, and their greatest diameter is 
•34 mm. The relation of the two anterior pairs of suckers to the parapodia may be 
seen in the specimen; they lie, with respect to the short axis of the body (fig. 25), outside 
the parapodia (a. and &.), but joined to them. It may therefore be safely concluded that 
the shorter diameter represents the longitudinal axis. The only opening that can 
represent the mouth falls within this line, between the two suckers and parapodia (fig. 25, 
a. and b.). This mouth opening is then rather dorsal in position (fig. 24, m.). I did not 
discover the cloacal opening. 
Host. — Pentacrinus alternicirrus, P. H. C., from Station 214 (south of Philip- 
pine Islands) of the Challenger Expedition. 
24. Myzostoma compressum, n. sp. (PI. III. figs. 4-8). 
This species is distinguished by its yellowish-brown colour and laterally compressed 
shape (see ideal section, fig. 7) ; the back runs up like a keel, which is considerably higher 
than the animal is broad. The skin of the back is quite smooth ; the margin of the body, 
as I observed in a specimen preserved by v. Willemoes Suhm, is provided with twenty cirri, 
resembling very closely in size those of Myzostoma coronatum ; the largest are '2 mm. long. 
